Yes, the Arditti set ought to be compulsory. And Tetras, Nomos Alpha and the rest ought to be on everyone's listening list.
Another awe-inspiring piece which I always mention because it's often forgotten is Synaphai; there's a very fine recording of it, but there's also a Japanese reading of it on youtube which makes the jaw drop.
And then there's X's Oresteia - an imagining of ancient Greek music which is echt-Xenakis, in its rawness and hyper-expressivity, its pushing instruments to their extremes and its return to real fundamentals, but which may surprise those who think Xenakis is just stochastic noise. It's full of melody - Xenakis could pen a tune very well, surprisingly! (For instance, I've only heard his Shaar once, and it was maybe two decades ago, but I can still remember its opening melodic line precisely!)